This invention relates to an air-cooled, reciprocating piston, internal combustion engine having at least two adjacent cylinder barrels on the crankcase thereof, and a plurality of cooling ribs lying substantially perpendicular to the longitudinal axes of the cylinder barrels on at least part of the periphery thereof. Cylinder heads on the cylinder barrels have inlet ports located on a cooling air inlet side thereof and exhaust ports on a cooling air outlet side thereof, and an air deflecting cover is mounted on the cylinder barrels at the cooling air outlet side thereof.
An air-cooled reciprocating piston internal combustion engine of the aforedescribed type is disclosed in a publication entitled "Luftgekuhlte Fahrzeugmotoren" by J. Mackerele, Frank'sche Verlagsbuchhandlung, Stuttgart, 1964, pages 171 to 173, describing a T 924 diesel made by Tatra-Werke CSSR. Such an engine has the entire periphery and length of the cylinder barrels provided with cooling ribs lying perpendicular to the longitudinal axes of the cylinder barrels, and being swept uniformly with cooling air from the inlet side thereof. The cooling air flowing laterally around and between adjacent cylinder barrels is passed, on the cooling air outlet side, by cooling air deflectors to a rear cooling rib area of the cylinder barrels on the outlet side.
Due to the position of the engine exhaust ports on the cooling air outlet side of this known arrangement, the rear areas of the cylinder barrels, on the cooling air outlet side, especially the cylinder barrel sections near the cylinder heads, are subjected to the highest thermal stresses. However, for the known reciprocating piston internal combustion engines, only the cooling air which has already been used for cooling the lateral peripheral areas, especially those near the cylinder heads of the cylinder barrels, and which have already therefore been heated, can be directed to such areas. Because of possible overheating, such a reciprocating piston internal combustion engine has only a limited output. In addition, and even if the power output is limited, since the flow of cooling air supplied must be adapted to the cooling air needed for cylinder barrel areas subjected to the highest thermal stress, excessive cooling cannot be avoided, under certain load conditions, at the front of the cylinder barrels at the air inlet side. This, in turn, gives rise to incomplete combustion and increased emission of pollutants.